Anatomical Development of Cell Structure Including Casparian Strip during Root Growth in Grapevines

Abstract

Morphological and anatomical changes in roots associated with their development were investigated in grapevines. When new roots initiated from the suberized structural root in grapevines, the tip of the root expanded outward and the suberized outer layer was detached from the surface of the root tip. At the onset of root initiation, the cell nucleus reappeared in the apical meristem, and cell division occurred. Once approximately five xylem vessels per pole had appeared, the Casparian strip appeared as a dot in the center of the radial wall of the endodermis. At a point 150 mm from the root tip, the endodermis was completely suberized and the number of xylem vessels per pole increased. In younger roots, suberization of the exodermis was observed earlier than in the endodermis, although the Casparian strip could not clearly be detected in the exodermis. As the root aged, a gap formed between the endodermis and pericycle. Before the endodermis was sloughed off from pericycle layers, cell division was observed in the pericycle and the suberized pericycle layers increased.